The present invention relates to electroluminescent polymers which comprise indenofluorenarylamine derivatives as recurring unit, to a process for the preparation thereof, to blends and formulations comprising these polymers, and to the use of these polymers or blends in electronic devices, in particular in organic light-emitting diodes, so-called OLEDs. The polymers according to the invention exhibit improved efficiency and a longer lifetime, in particular on use in OLEDs.
Conjugated polymers have already been investigated intensively for a long time as highly promising materials in OLEDs. OLEDs which comprise polymers as organic materials are frequently also known as PLEDs (PLED=polymer light-emitting diode). Their simple preparation promises inexpensive production of corresponding light-emitting diodes.
Since PLEDs usually only consist of one light-emitting layer, polymers are required which are able as far as possible to combine all functions (charge injection, charge transport, recombination) of an OLED in themselves. In order to meet these requirements, different monomers which take on the corresponding functions are employed during the polymerisation. Thus, it is generally necessary, for the generation of all three emission colours, to copolymerise certain comonomers into the corresponding polymers (cf., for example, WO 00/46321 A1, WO 03/020790 A2 and WO 02/077060 A1). Thus, it is possible, for example, starting from a blue-emitting base polymer (“backbone”), to generate the other two primary colours red and green.
Various classes of material, such as, for example, poly-para-phenylenes (PPPs), have already been proposed or developed as polymers for full-colour display elements (full-colour displays). Thus, for example, polyfluorene, polyspirobifluorene, polyphenanthrene, polydihydrophenanthrene and polyindenofluorene derivatives come into consideration. Polymers which comprise a combination of the said structural elements have also already been proposed.
The most important criteria of an OLED are efficiency, colour and lifetime. Since these properties are crucially determined by the emitter(s) used, improvements in the emitters compared with the materials known from the prior art are still necessary.
In particular, the lifetime of green- and especially blue-emitting polymers is not yet ideal for many applications.
Polymers which comprise aryl-substituted trans-indenofluorene derivatives as recurring units are disclosed, for example, in WO 2004/041901 A1.
Polymers which comprise indenofluorenediamine derivatives as recurring units are likewise known. Such polymers are disclosed, for example, in WO 2005/104263 A1. A disadvantage of these polymers comprising indenofluorenediamine units is that they only facilitate a pale-blue emission colour.